1. Field of the Invention
The present invention relates to a chain structure, for example, employed in a sludge scraper which is provided in a settling pond of a sewage disposal facility.
2. Description of the Conventional Art
The sludge scraper is provided within a sewage disposal tank in a first settling pond or a final settling pond of the sewage disposal facility, and is structured such as to scrape the sludge constituted by various components which are piled up in a bottom of the sewage disposal tank to one side in the bottom of the sewage disposal tank by a sludge scraping plate. The sludge scraped by the sludge scraper as mentioned above is sucked out by a pump, and is carried out to a treatment facility in the next step in an outer portion of the sewage disposal tank.
FIGS. 14 to 18 are views which are referred for describing a conventional chain structure 2 which is used in the sludge scraper installed within the sewage disposal tank.
The conventional chain structure 2 is structured, as shown in FIG. 14, such as to have a drive sprocket wheel 6, driven sprocket wheels 8, 10 and 12, an endless chain 4 which is wound around the sprocket wheels 6, 8, 10 and 12, and a plurality of flight plates 14 (sludge scraping plates) which are provided so as to protrude to an outer side at predetermined distances in a length direction of the chain 4 (refer to Japanese Unexamined Patent Publication No. 2002-273105).
In FIG. 14, the chain 4 and the sprocket wheels 6, 8, 10 and 12 are shown only one set, however, individual parts of the other set of chain 4 and sprocket wheels 6, 8, 10 and 12 having the same structures are provided at a position which is away from each other in a vertical direction to a paper surface in the drawing, in inner sides of side surfaces facing to each other of a sewage disposal tank 3 so as to face to each other.
Further, since each of the flight plates 14 is fixed in its inner side in a width direction in its both end portions to an outer peripheral side of each of a pair of chains 4, the flight plate 14 is circularly moved in an outer side of the chain 4 integrally with the chain 4 in conformity to a circular movement of the chain 4 in a length direction (a clockwise direction in FIG. 14), on the basis of a rotating motion of the drive sprocket wheel 6.
Then, the flight plates 14 move in a direction of a leftwards arrow in the drawing so as to be along a bottom surface 3a of the sewage disposal tank 3 when the flight plates 14 moves in a lower portion in FIG. 14, and scrape and collect the sludge piled up on the bottom surface 3a to a sludge storage portion 3b in a left end portion side in the drawing.
The sprocket wheel 6 of the conventional chain structure 2 mentioned above has been constructed, as shown in FIG. 15B, by a cylindrical boss portion 6b which has a shaft hole 6a penetrating in an axial direction (a lateral direction in the drawing), and a disc portion 6e which is arranged in a center portion in the axial direction of the boss portion 6b and forms a gear tooth forming portion 6c in an outer peripheral portion in a radial direction (a vertical direction in the drawing).
Further, an annular projection portion 6d is integrally formed in an inner side in the radial direction than the gear tooth forming portion 6c in the disc portion 6e of the sprocket wheel 6. The annular projection portion 6d has a height toward outer sides in a thickness direction from the disc portion 6e, has its axis in common with the axis of the shaft hole 6a and is formed as a circular ring shape.
Further, as shown in FIG. 15A, in the gear tooth forming portion 6c of the sprocket wheel 6, a tooth top portion 6f (a convex portion) and a tooth bottom portion 6h (a concave portion) are alternately formed in a circumferential direction of the gear tooth forming portion 6c via an engagement portion 6i of these step portions.
The sprocket wheel 6 is structured, as shown in FIG. 17, such that a rotating shaft 16 attached to the shaft hole 6a so as to be relatively non-rotatable via a key 17 is driven by a drive device, for example, a motor (not shown) so as to rotate around an axis thereof.
The chain 4 is structured, as shown in FIG. 16, such that a pair of inner link plates 18 and a pair of outer link plates 20 are alternately coupled in a length direction, however, a pair of link plates 26 with attachments (corresponding to a side plate member) integrally provided with attachments 28 (a flight plate attaching portion) are coupled at appropriate distances, as shown in FIG. 17.
The link plate 26 is structured such that the flight plate 14 formed as an approximately C-shaped form in its cross sectional shape is fixed to the attachment 28 via a spacer 30 by a screw fastening means using bolts and nuts.
Further, the conventional chain structure is structured, as shown in FIG. 18, such that a pair of chains 4 provided with the attachments 28 as mentioned above are respectively wound around a pair of sprocket wheels 6 which are arranged at positions which are away from each other in a lateral direction of the drawing so as to be faced to each other. Further, a pair of chains 4 are respectively wound around a pair of sprocket wheels 8, 10 and 12 one of which is shown in FIG. 14.
A plurality of flight plates 14 are provided as mentioned above in a pair of chains 4 and 4 which are arranged so as to be faced to each other at predetermined distances in a length direction thereof. The flight plate 14 is formed as a long shape having a length in an approximately vertical direction to the length direction of the chain 4, that is, a vertical direction to a paper surface in FIG. 14, and both end portions in the length direction are respectively attached to respective outer peripheral sides of a pair of chains 4 and 4.
Further, the flight plate 14 is structured, as shown in FIG. 18, such that shoes 36 and 37 are respectively fixed to an upper portion and a lower portion of the drawing in both end portions in the length direction.
Among the shoes 36 and 37, the shoe 36 provided in the lower portion in FIG. 18 of the flight plate 14 is structured such that the shoe 36 comes into contact with an upper surface of a rail member 32 which is provided on a rail support member 34 extending in a horizontal direction to the sprocket wheel 6 side from a vertical wall surface (not shown) in the sewage disposal tank 3 and guides the flight plate 14 along the rail member 32, when the flight plate 14 moves in the upper portion in FIG. 14.
On the other hand, the shoe 37 provided in the upper portion in FIG. 18 of the flight plate 14 is structured such that the shoe 37 comes into contact with an upper surface of a pond bottom rail (not shown) which is provided on the bottom surface 3a of the sewage disposal tank 3 and guides the flight plate 14 along the pond bottom rail, when the flight plate 14 moves in the lower portion in FIG. 14.
Further, as shown in FIG. 18, a pair of sprocket wheels 6 arranged so as to face to each other are provided with a single rotating shaft 16 which is attached to each of the shaft holes 6a so as to be relatively non-rotatable via the key 17 as shown in FIG. 17. The rotating shaft 16 is driven by the drive device, for example, the motor (not shown), and rotates a pair of sprocket wheels 6 so as to be synchronous with each other.